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Mystery cirrate octo

Clem

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Via the NZ antarctic fisheries observer known as hud2, he of the previously unknown M. Hamiltoni specimen, come these shots of a striking cirrate octopus.

(Above images courtesy of and wholly owned by hud2)

According to hud2, this gelatinous octopus was recovered from the stomach of a Patagonian toothfish, which makes the preservation of the specimen all the more remarkable, and suggests that toothfish might not be biters so much as gulpers. I can't think of any other explanation for the excellent condition of the thing. I talked about this one with OB, and we thought we were looking at a decapod, but what we took for an extra pair of arms was the animals umbrella-like webbing. The skin has separated from the mantle, which is nearly as transparent as the arms, and one fin can be seen. The measuring marks must be centimeters, and they are clearly visible through the arms...amazing transparency. The eyes are very well-defined, dark and barrel-shaped, and the arms present both cirri and small suckers not on stalks.

This and other specimens were sent to Te Papa museum in NZ, so it's possible that Bald Tank Man himself has already ID'd it, but I'm going to throw out Stauroteuthis gilchristi as a possibility. It's a good-looking match, anyhow, the morphology being very similar, and S. gilchristi is known from South Georgian and sub-South African locales. On the other hand, the gut of the mystery cirrate appears to show a large caecum which I don't see on the S. gilchristi drawing, and the mystery cirrate's suckers appear to be smaller.

A beautiful thing, whatever it is. Many thanks to hud2 for his generosity, and for allowing me to post these.

Clem
 

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DWhatley

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Very cool (what a great contact, hope he sends more your/our way). What excited me about it though was the skin "separation" from the mantle. I have seen this and wondered about it in O.briareus (at death).
 

Clem

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What's your take on the skin separation, D? I doubt it's the result of early-stage digestive processes in the toothfish, so perhaps it's the result of something mechanical, i.e. uniform pressure applied by the esophagus to the mantle as the octo went "down the hatch," or the toothfish generated sufficient suction to pull the skin away before the octo was swallowed. Where have you seen this?

Clem
 

DWhatley

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I wonder if the coldwater animal was a newly spent postbrood female. Biology is not my strong suit but my impression was that perhaps the skin is not connected to the mantle. Kooah suffered no death trama other than egg bearing/brooding (do you know if this one is male or female?) so I wondered if it was just more apparent in post brood females. However, KaySoh did not show this separation. She did not have hatchlings but her mantle was hugely extended and we believe she laid (and did sequester herself expectantly) infertile eggs (I did not see them though). SueNami (male - no final photo taken), did not show this separation, or I did not notice it. You can see the separation fairly clearly in Kaysoh's photo link. It was quite pronounced and difficult to set up the picture because of the sliding.
 

Tintenfisch

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Wow, that specimen is in AMAZING condition, all the more so for its origin! I will poke Steve with a sharp stick and see whether I can get him to respond. We have a bunch of photos (and specimens) of Antarctic cephs that we are working through, and this looks familiar.
Clem, are you sure the skin is actually separated from the mantle? Some species have a really thick, gelatinous layer around the outside that looks very similar to this when they are lying on a flat surface. Sometimes this is only true at small stages (Cycloteuthis sirventyi is one that springs to mind - you can kind of see what I mean in the bottom illustration; gelatinous bolitaenid octos also have it). This really threw me off the first time I encountered it.
 

DWhatley

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Kat,
Blow up Kooah's final photo. This is a Common Caribbean octopus (O. briareus and not gelatinous). The separation was very noticable and the outer skin definitely slipped around separately from the mantle (making positioning it hard for photographing).
 

Tintenfisch

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D, sorry, was just trying to clarify what we're looking at here. I interpreted 'separated' as 'torn away from' (like over the arms, where you can see red skin peeled back to reveal white muscle underneath), whereas the gelatinous skin/tissue over the mantle in these photos looks loose enough to move independently of the much smaller, visible cone of muscle underneath, without actually being detached from it.

Off to bother Steve now.
 

Clem

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Tintenfisch;177176 said:
D, sorry, was just trying to clarify what we're looking at here. I interpreted 'separated' as 'torn away from' (like over the arms, where you can see red skin peeled back to reveal white muscle underneath), whereas the gelatinous skin/tissue over the mantle in these photos looks loose enough to move independently of the much smaller, visible cone of muscle underneath, without actually being detached from it.
T,

I actually hadn't given that much thought to using the word "separated," but I was interpreting the photo as showing integument that had been pulled away from the muscle post-mortem, and not as a separate gelatinous envelope. I thought that the presence of chromatophores indicated skin, and I don't know what the other side looked like or how much arranging of the thing took place before being photographed. The whiteness of the two arms on top was one of the things that made me think we were looking at a decapod: I thought they were tentacles, more muscular and therefore more opaque.

You could poke Steve with a sharp stick, or dangle a bottle of Just For Men hair-coloring in front of him. Whichever works best for you.

Clem
 

Tintenfisch

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Clem;177180 said:
You could poke Steve with a sharp stick, or dangle a bottle of Just For Men hair-coloring in front of him.
I am still hoping it evolves to bright blue... right now he looks kind of like Zuse from TRON: Legacy. With a beard. And not in a good way. :hmm:

I think the width of the gelatinous, red-skin-covered layer is possibly just the 'slump' that comes from spreading a thick, cylindrical, neutrally buoyant object onto a flat surface out of water, as in the attached (extremely crude) diagram. But there may also be detachment; as you say, we can only see the 2D image and with no chance to manipulate, we do have to guess at some details. The impression is also maybe further distorted by the fact that we're looking at a right-lateral view of the animal, with the gelatinous layer spread out so far dorsally that it has sort of smeared the fins into a strange orientation. The overall coloration and tissue appearance does look like S. gilchristi to me, but then the gelatinous layer is WAY thicker than I've ever seen for that species.
 

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